Summary A Bell 205A-1 helicopter, registrationC-FMQN, serial number30082, was engaged in forest fire suppression activities and was bucketing the southwest corner of a fire. The pilot had already made several drops on the day of the occurrence. While the helicopter was approximately 250feet above ground level en route to TobinLake, Saskatchewan, to pick up a bucket of water, the engine fire warning light came on and the pilot saw smoke coming out of the engine cowling. Seconds later, the pilot noted that the master caution light and the engine chip detector had illuminated, and the oil pressure was decreasing to zero. The pilot elected to land the helicopter in a farmer's field. During the descent, the pilot kept power on the engine and discharged the fire bottle, but the fire did not extinguish. Immediately after the landing, the pilot shut the fuel off and, with the second crew member, evacuated the aircraft. Another helicopter working the same fire dropped a bucket of water and extinguished a majority of the fire. The rest of the fire was extinguished using a fire truck that arrived on the site. The helicopter sustained substantial damage to the engine, engine bay, and baggage compartment. The crew members were not injured. Ce rapport est galement disponible en franais. Other Factual Information The accident occurred during daylight hours at about 2000 central standard time1. The observed weather at 2000 at PrinceAlbert, 67miles southwest of TobinLake, was as follows: winds 200degrees at 13knots, visibility 15statute miles, scattered clouds at 6000feet, broken clouds at 14000feet, temperature 18C, dew point 8C, and altimeter setting 29.92inches of mercury. Similar conditions existed at TobinLake at the time of the accident, except that the wind was from the east at 5 to 10knots. The pilot of the helicopter held a valid commercial helicopter pilot licence and was properly trained and qualified for the intended flight. The helicopter was operated by Campbell Helicopters Ltd., and was on contract to the Province of Saskatchewan to help fight forest fires in the area. The helicopter underwent some maintenance, including major repairs to the engine deck and firewall, approximately six weeks before the accident. The aircraft had flown 19.9hours since the last 100-hourinspection. At 13.5flight hours prior to the occurrence, the starter/generator had been removed to accommodate the replacement of the starter/generator seal, then re-installed. Photo1. Subject fuel line was installed on another similar engine to show routing Inspection of the engine revealed extensive damage to the engine and surrounding engine bay area. The blown fire bottle plug and fire retardant material found in the engine bay indicated that the fire retardant had been discharged. The variable inlet guide vane actuator (VIGVA) hose, which provides fuel pressure to open the variable guide vanes, was found pinched between the top of the starter/generator and the impeller housing assembly (seePhoto1). Further inspection of the pinched fuel hose revealed a hole through the steel braiding and inner lining (seePhoto2). Inspection of three similar helicopters, found that both lines coming from the VIGVA were routed behind and underneath the starter/generator, clear of any interference.The fire was confined to the engine bay and the baggage compartment, which is directly underneath the engine bay deck. All engine indication electrical harnesses and interfaces were destroyed by the fire. The cap that houses the cooling fan on the starter generator had separated from the generator housing. The cap was retained over the cooling fan by the pinched fuel line. The cooling fan blades were missing. The cap is normally held in place by six countersunk screws on the rear of the starter/generator. Removal of the starter/generator revealed that the hold-down nut at the 12o'clock position was missing, and the hold-down nut at the 10o'clock position was backed off approximately 0.125inch. It was reported that the retaining nut at the 12o'clock position had been intentionally left off for ease of starter/generator removal and installation. The end of the starter/generator shaft showed signs of peening, indicating misalignment. The commutator and brushes of the starter/generator produce heat and sparks during normal operation. The starter/generator and fuel hose assembly were forwarded to the TSB Engineering Branch Laboratory for analysis. The analysis revealed soot on the shoulders of the hold-down nut receptacles, on the attach flange of the starter/generator, at the12,10 and 8o'clock positions. The starter/generator is normally held in place by six hold-down nuts. Analysis of the cooling fan indicated that the fan blades had been abraded away. No indication of a catastrophic failure of the fan blades was found. Analysis of the fuel hose indicates that the steel braid strands failed as a result of chafing.